To understand the path of the comet through space, it will be sufficient to examine carefully the accompanying chart [above]. It represents the comet coming from infinite space obliquely towards the Earth, and afterwards falling into the Sun which does not arrest it in its passage toward perihelion. No account has been taken of the perturbation caused by the Earth’s attraction, whose effect would be to bring the comet nearer to the Earth’s orbit. All the comets which gravitate about the Sun—and they are numerous—describe similar elongated orbits—ellipses, one of whose foci is occupied by the solar star. The drawing [below] gives an idea of the intersections of the cometary and planetary orbits, and the orbit of the Earth about the Sun. On studying these intersections, we perceive that a collision is neither an impossible nor an abnormal event.
The comet was now visible to the naked eye. On the night of the new moon, the atmosphere being perfectly clear, it had been detected by a few keen eyes without the aid of a glass, not far from the zenith near the edge of the Milky Way to the south of the star Omicron in the constellation of Andromeda, as a pale nebula, like a puff of very light smoke, quite small, almost round, slightly elongated in a direction opposed to that of the Sun—a gaseous elongation, outlining a rudimentary tail. This, indeed, had been its appearance since its first discovery by the telescope. From its inoffensive aspect no one could have suspected the tragic role which this new star was to play in the history of humanity. Analysis alone indicated its march toward the Earth.
But the mysterious star approached rapidly. The very next day the half of those who searched for it had detected it, and the following day only the nearsighted, with eyeglasses of insufficient power, had failed to make it out. In less than a week everyone had seen it. In all the public squares, in every city, in every village, groups were to be seen watching it, or showing it to others.
Day by day it increased in size. The telescope began to distinguish distinctly a luminous nucleus. The excitement increased at the same time, invading every mind. When, after the first quarter and during the full moon, it appeared to remain stationary and even to lose something of its brilliancy, as it had been expected to grow rapidly larger, it was hoped that some error had crept into the computations, and a period of tranquillity and relief followed. After the full moon the barometer fell rapidly. A violent storm-center, coming from the Atlantic, passed north of the British Isles. For twelve days the sky was entirely obscured over nearly the whole of Europe.
Once more the Sun shone in purified atmosphere, the clouds dissolved and the blue sky reappeared pure and unobscured; it was not without emotion that men waited for the setting of the Sun—especially as several aerial expeditions had succeeded in rising above the cloud-belts, and aeronauts had asserted that the comet was visibly larger. Telephone messages sent out from the mountains of Asia and America announced also its rapid approach. But great was the surprise when at nightfall every eye was turned heavenward to seek the flaming star. It was no longer a comet, a classic comet such as one had seen before, but an aurora borealis of a new kind, a gigantic celestial fan, with seven branches, shooting into space seven greenish streamers, which appeared to issue from a point hidden below the horizon.
No one had the slightest doubt but that this fantastical aurora borealis was the comet itself, a view confirmed by the fact that the former comet could not be found anywhere among the starry host. The apparition differed, it is true, from all popularly known cometary forms, and the radiating beams of the mysterious visitor were, of all forms, the least expected. But these gaseous bodies are so remarkable, so capricious, so various, that everything is possible. Moreover, it was not the first time that a comet had presented such an aspect. Astronomy contained among its records that of an immense comet observed in , which at that time had been the subject of much discussion, and whose picturesque delineation, made de visu by the astronomer Chèzeaux, at Lausanne, had given it a wide celebrity. But even if nothing of this nature had been seen before, the evidence of one’s eyes was indubitable.
Meanwhile, discussions multiplied, and a veritable astronomical tournament was commenced in the scientific reviews of the entire world—the only journals which inspired any confidence amid the epidemic of buying and selling which had for so long a time possessed humanity. The main question, now that there was no longer any doubt that the star was moving straight toward the Earth, was its position from day to day, a question depending upon its velocity. The young computor of the Paris observatory, chief of the section of comets, sent every day a note to the official journal of the United States of Europe.
A very simple mathematical relation exists between the velocity of every comet and its distance from the Sun. Knowing the former one can at once find the latter. In fact the velocity of the comet is simply the velocity of a planet multiplied
